1. Field
This application relates generally to wireless communication and, in various aspects, to inter-pulse duty cycling, a duty cycling power scheme, sub-packet communication, and wireless communication between a wireless device and multiple peripherals.
2. Background
Wireless communication systems may be designed to support various end uses. Here, one or more tradeoffs may be made in terms of coverage area, communication bandwidth, data transfer rate, ease of connectivity, power consumption, and other system parameters. For example, a cellular telephone network may be optimized to provide wireless coverage over a very wide area and provide ease of connectivity. In contrast, a wireless local area network such as a Wi-Fi network may be optimized to provide high speed connectivity, at the expense of the size of the wireless coverage area and perhaps the ease of connectivity. A wireless body area network or a wireless personal area, on the other hand, may be optimized to provide low power consumption, which may be achieved through the use of an even smaller wireless coverage area.
As an example of the latter form of network, a wireless personal area network may provide connectivity for devices in a home or a small office or may be used to provide connectivity for devices carried by a person. In a typical scenario, a wireless personal area network may provide connectivity for devices within a range on the order of 30 meters. In some applications, one or more of the devices that make up a wireless personal area network may be portable devices. For example, a cell phone may communicate with a headset via a wireless personal area network such as Bluetooth.
In general, it is desirable to reduce the power consumption of such portable devices. For example, a device that consumes less power may utilize a smaller battery or may require less frequent battery recharges or battery replacements. In the former scenario, the device may potentially be manufactured in a smaller form factor and at a lower cost. In the latter case, the device may be more convenient for a user to use or may provide a lower overall cost of ownership.
Some personal area networks such as Bluetooth (e.g., IEEE 802.15.1) and Zigbee (e.g., based on IEEE 802.15.4) may employ power-down strategies to reduce the overall power consumption of a device. For example, after a device transmits or receives a packet, the device may power down certain portions of the device (e.g., the radio) for a certain period of time. Here, on the transmit side the device may remain in a low power state until there is another packet to send. Conversely, on the receive side the device may awake from a low power state at regular intervals to determine whether another device is attempting to transmit data.
It also may be desirable to employ low power devices in certain body area network applications. In a typical configuration, a body area network may provide connectivity between devices that are worn or carried by a person, or are incorporated into or placed within a vehicle, a room or some other relatively smaller area. Thus, a body area network may provide a wireless coverage area on the order of 10 meters in some implementations. In some applications the devices that make up a body area network may be portable devices or may preferably be relatively low maintenance devices. Consequently, devices that consume relatively small amounts of power may be advantageously employed in these and other types of applications.